From Sahaja Yoga Encyclopedia

Pir is the spirit or atma as described by Mohammed.

In Persian, Pir is used to refer to a Sufi master or spiritual guide.

From Wikipedia

Pir or Peer (Persian: پیر‎‎, literally "old [person]") is a title for a Sufi master or spiritual guide equally used in the nath tradition. They are also referred to as a Hazrat or Shaikh, which is Arabic for Old Man. The title is often translated into English as "saint" and could be interpreted as "Elder". In Sufism a Pir's role is to guide and instruct his disciples on the Sufi path. This is often done by general lessons (called Suhbas) and individual guidance. Other words that refer to a Pir include, Murshid (Arabic: مرشد‎‎, meaning "guide" or "teacher"), Sheikh and Sarkar (Persian word meaning Master, Lord).

The title Peer Baba (पीर बाबा) is common in Hindi and is used to give a salutation to Sufi masters or similarly honored persons. After their death people visit their tombs (dargah) (मकबरा).